1. Field of the Invention
This invention relates to a Wing-in-Ground effect (WIG) vehicle and more particularly to a WIG vehicle having a power augmentor along the leading edge of the wings.
2. Description of the Prior Art
Ground effect vehicles include any device which travels on a cushion of air which is trapped beneath the body of the vehicle. Some of the more common forms of ground effect machines include hovercraft which have even become commercially feasible. A less common form of ground effect machine is an aircraft which traps an air cushion under its wings. This vehicle is referred to as a Wing-in-Ground effect (WIG) vehicle.
Since the first WIG device was designed in 1935, various attempts have been made to develop a feasible WIG machine. Traditionally, the air trapped under the wing is the result of the aircraft moving forward utilizing a ram effect to produce enough pressure to form an air cushion. This ram effect was utilized in the device shown in U.S. Pat. No. 3,135,480 to create the cushion of air necessary to lift the aircraft. This device also used the efflux from the propulsion system to create a "curtain" of air to contain the cushion in place of a rigid end plate. When the device is hovering, there is no ram force and most of the propulsion efflux is used to create the cushion. In the hovering mode, a great deal of efflux is required to offset the weight of the aircraft, in the same manner as a hovercraft.
Another WIG vehicle is shown in U.S. Pat. No. 4,151,893. As shown in FIG. 16 of this patent, the efflux of the engines may be used to provide a cushion of air or a ram effect may be used when moving at a sufficient velocity. Both this device and the device described in the previous paragraph use the propulsion efflux in the hover mode, but a relatively large amount of energy is expended for this purpose.
Another type of aircraft using ground effect is shown in U.S. Pat. Nos. 3,124,322 and 3,412,956. While these aircraft fly in a normal aerodynamic mode most of the time, a ground effect procedure is used in landing and taking off. The efflux is carried by conduits to a series of slot-like openings on the bottom of the wing and fuselage. The efflux is blown downwardly through the slots to form a ground effect cushion. This vehicle does not use WIG concepts when flying, but when utilizing these concepts at takeoff and landing, is subject to the same problems as the two previously mentioned devices.
A more recent advance in WIG design avoids the necessity for such massive amounts of efflux to create the ground effect. The Power-Augmented Ram Wing-in-Ground Effect Vehicle (PAR-WIG), shown in FIG. 1, utilizes the efflux from the aircraft engines to form the air cushion during the entire flight of the aircraft. The engines are placed near the front of the vehicle and tilted so that the efflux blows under the front edge of each wing 12. The efflux is partially trapped under the wing by end plates 14 and movable trailing edge 16. A static pressure rise results under the wing, providing lift for the vehicle. The amount of lift is greater than the prior art devices due to the design of the propulsion system which entrains ambient air, hence filling the volume under the wing with high energy air. Tests have shown that the PAR-WIG cushion can be used with high wing loadings and relatively rough sea conditions, but requires relatively low thrust. Thus, this design is a large improvement over previous models. This design presents new problems, however, by the mounting of the engines near the nose of the aircraft. The engines are very vulnerable to the ingestion of salt spray and debris, both of which may damage the engines. Also, the structure of the aircraft must be more substantial in the nost section, causing an undesirable weight increase.